railroad

Freight cars

Throughout the world the great majority of freight cars for all rail gauges are built with four axles, divided between two trucks. Because of the layout constraints of some freight terminals, several European railroads still purchase a proportion of two-axle vehicles, but these have a much longer wheelbase and hence a considerably larger load capacity than similar cars in the past. Some bulk mineral cars in Germany and the United States have been built with two three-axle trucks, and Russia and various other former Soviet states still have a number of freight cars carried on four two-axle trucks; these are the world’s largest. Concern to maximize payload capacity in relation to tare vehicle weight has led to U.S. and European adoption of articulation for cars in certain uses, notably intermodal transport. In this system a car comprises several frames or bodies (usually not more than five), which, where they adjoin, are permanently coupled and mounted on a single truck.

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One type of vehicle that is virtually extinct is the caboose, or brake-van. With modern air-braking systems, the security of a very long train can be assured by fixing to its end car’s brake pipe a telemetry device that continually monitors pressure and automatically transmits its findings to the locomotive cab.

Before World War II, freight cars consisted almost entirely of four basic types: the semiwalled open car, the fully covered boxcar, the flatcar, and the tank car. Since then, railroads and car builders have developed a wide range of car types designed specifically for the ideal handling and competitive transport of individual goods or commodities. At the same time, the payload weight of bulk commodities that can be conveyed in a single car without undue track wear has been significantly increased by advances in truck design and, in North America, by growing use of aluminum instead of steel for bodywork, to reduce the car’s own tare weight. In Europe and North America, where highway competition demands faster rail movement of time-sensitive freight, cars for such traffic as perishable goods, high-value merchandise, and containers are designed to run at 120 km (75 miles) per hour. The French and German railways both operate some selected merchandise and intermodal trains at up to 160 km (100 miles) per hour to achieve overnight delivery between centers up to about 1,000 km (600 miles) apart. In the United States, container trains traveling at 120 km/hr where route characteristics allow are scheduled to cover about 3,500 km (2,200 miles) in 52 hours.

In Europe and North America open cars for bulk mineral transport are generally designed for rapid discharge, either by being bodily rotated or through power-operated doors in the floor or lower sides of their hopper bodies. Modern North American four-axle coal cars typically have 100–110 tons’ payload capacity. In Europe, where tighter clearances necessitate smaller body dimensions and track is not designed for axle loadings as high as those accepted in North America, the payload capacity of similar four-axle cars is between 60 and 65 tons. High-sided open cars also are built with fully retractable sliding roofs, either metal or canvas, to facilitate overhead loading and discharge of cargoes needing protection in transit. In a variant of this concept for the transport of steel coil in particular, the sidewalls and roof are in two or more separate, integral, and overlapping assemblies; these can be slid over or under each other for loading or discharge of one section of the vehicle without exposing the remainder of the load.

Fully covered hopper cars or tank cars are available with pressure discharge for bulk movement of a variety of powders and solids. Tank cars are also purpose-designed for safe transport of a wide range of hazardous fluids.

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Because of the rapid growth of intermodal transport in North America, boxcar design has seen fewer changes there than in western Europe. For ease of mechanized loading of palletized freight, modern European boxcars are built with their entire sidewalls divided into sliding and overlapping doors. Another option is to replace the sidewalls with a fully retractable, material-covered framework, so that the interior of the vehicle can be wholly opened up for loading or discharge. A typical North American boxcar for bulky but comparatively light cargo may have a load-area volume of up to 283 cubic meters (10,000 cubic feet); that of a modern four-axle European boxcar is 161.4 cubic meters (5,700 cubic feet). Boxcars are often fitted internally with movable partitions or other special fittings to brace loads such as products in sacks. Vehicles for transport of fragile merchandise have cushioned draft gear that absorbs any shocks sustained by the cars in train or yard shunting movement.

The automobile industry’s concentration of manufacture of individual models at specific plants has increased the railroads’ share of its transportation. As distances from manufacturing plant to dealer increase—and in many cases these involve international transits—the security and economy offered by the railroad as a bulk transporter of finished autos have become more appreciated. In North America vertical clearances allow automobiles to be carried in triple-deck freight cars, but in Europe the limit is double-deck. Retractable flaps enable each deck of adjoining cars to be connected to form drive-through roadways on both levels for loading and discharge of an auto-transporter train. Such cars also are used for a type of service for motorists that is widespread in Europe but confined to one route in the United States: trains that combine transporters for autos with passenger cars for their occupants. These are mostly operated between ports or inland cities and vacation areas in the peak season. Special-purpose cars also have been developed for inter-plant movement of automobile components, including engines and body assemblies, and for regular delivery of spare parts to distribution areas.